Replace pkg_resources with importlib.resources for Python 3.14 compatibility

ebook_converter/ebooks/conversion/plugins/rtf_input.py

@@ -1,6 +1,6 @@
 import glob
 import os
-import pkg_resources
+from importlib.resources import files
 import re
 import textwrap
 
@@ -288,8 +288,8 @@ class RTFInput(InputFormatPlugin):
 
         self.log.info('Converting XML to HTML...')
         inline_class = InlineClass(self.log)
-        with open(pkg_resources.resource_filename('ebook_converter',
-                                                  'data/rtf.xsl')) as fobj:
+        with open(str(files('ebook_converter')
+                      .joinpath('data/rtf.xsl'))) as fobj:
             styledoc = etree.fromstring(fobj.read())
         extensions = {('calibre', 'inline-class'): inline_class}
         transform = etree.XSLT(styledoc, extensions=extensions)